Fastener driving tool

ABSTRACT

THERE IS PROVIDED A FASTENER DRIVING TOOL OF THE TYPE INCLUDING A DRIVE PISTON SLIDABLY MOUNTED WITH A MAIN CYLINDER AND MOVABLE THROUGH A DRIVE STROKE BY THE SUPPLY OF PRESSURIZED FLUID ABOVE THE PISTON AND MOVABLE THROUGH A RETURN STROKE BY THE EXHAUST OF THE CYLINDER ABOVE THE DRIVE PISTON. METERED PASSAGE MEANS ARE PROVIDED THROUGH THE PISTON TO PROVIDE A POSITIVE HEAD OF PRESSURE BELOW THE PISTON DURING THE RETURN STROKE OF THE PISTON, THEREBY PREVENTING INGESTION OF DUST-LADEN CONTAMINATED OUTSIDE AIR. IN ADDITION, THE FASTENER DRIVING TOOL IS PROVIDED WITH AN IMPROVED MAGAZINE CONSTRUCTION FORMED OF SHEET METAL HAVING A TRACK FOR SUPPORTING THE HEADS OF NAIL TYPE FASTENERS. THE STRIPS OF FASTENERS ARE LOADED THROUGH AN OPENING IN THE REAR OF THE MAGAZINE ASSEMBLY AND ARE ADVANCED TOWARD THE DRIVE TRACK OF THE DEVICE BY A PUSHER WHICH MAY BE PULLED BACK AND CAMMED OVER A STRIP OF FASTENERS INSERTED INTO THE MAGAZINE UNTIL IT PICKS UP THE LAST FASTENER OF THE STRIP. IN ADDITION, THE FASTENER DRIVING TOOL IS PROVIDED WITH A PROJECTION WHICH LOCKS A SAFETY MEMBER UPON DEPLETION OF THE FASTENERS WITHIN THE MAGAZINE ASSEMBLY TO A PREDETERMINED POINT.

Oct. 26, 1971 OBERGFELL ETAL 3,615,049

FASTENER DRIVING TOOL 5 Sheets-Sheet 1 Filed Sept. 1.5, 1969 f A u .0 mt 2.

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6 ZOE NE 02 vow NON vv L W SLE fl w R E L A a ,Y R WEDN H NB H l A m o 00 R Du ZU H LED A R E Oct. 26, 1971 Filed Sept. 15. 1969 ET AL 5 Sheets-Sheet 2 1 FIG. 3

INVENTORS'.

, RICHARD H. DOYLE EDWARD J. NOVAK Oct. 26, 1971 A. R. OBERGFELL EIAL I FASTENER DRIVING TOOL Filed Sept 15, 1969 5 Sheets-Sheet FIG.5

IIIIIIIIIIIIIIIIA'III a ALLEN R. OBERGFELL RICHARD H. DOYLE EDWARD J. NOVA .NVENTQRS:

' Oct. 26, 1971 A. R. OBERGFELL ETAL 5 9 I FASTENER DRIVING TOOL Filed Sept 15. 1969 5 Sheets-Sheet 4,

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I ATT'YS ALLENROBERGFELL v RICHARD H. DOYLE Oct. 26, 197.1 A. R. OBERGFELL ET AL 1 9 FASTENER DRIVING TOOL Filed se als, 1969 5 Sheets-Sheet a "INVENTORS: ALLEN ROBERGFELL RICHARD H. DOYLE EDWARD J. NOVAK' United States Patent 3,615,049 FASTENER DRIVING TOOL Allen R. Obergfell, Park Ridge, Edward J. Novak, Franklin Park, and Richard H. Doyle, Mount Prospect, Ill., assignors to Fastener Corporation, Franklin Park, Ill.

Filed Sept. 15, 1969, Ser. No. 857,930 Int. Cl. B27f 7/06 U.S. Cl. 227-8 Claims ABSTRACT OF THE DISCLOSURE There is provided a fastener driving tool of the type including a drive piston slidably mounted within a main cylinder and movable through a drive stroke by the supply of pressurized fluid above the piston and movable through a return stroke by the exhaust of the cylinder above the drive piston. Metered passage means are provided through the piston to provide a positive head of pressure below the piston during the return stroke of the piston, thereby preventing ingestion of dust-laden contaminated outside air. In addition, the fastener driving tool is provided with an improved magazine construction formed of sheet metal having a track for supporting the heads of nail type fasteners. The strips of fasteners are loaded through an opening in the rear of the magazine assembly and are advanced toward the drive track of the device by a pusher which may be pulled back and cammed over a strip of fasteners inserted into the magazine until it picks up the last fastener of the strip. In addition, the fastener driving tool is provided with a projection which locks a safety member upon depletion of the fasteners Within the magazine assembly to a predetermined point.

The present invention relates to an improved fastener driving tool, and more particularly, to a fastener driving tool having an improved main piston assembly and magazine assembly.

Commercial fastener driving tools are known wherein a drive piston is slidably mounted within the main cylinder of the tool, with a fastener driving blade mounted to the piston and slidable within a drive track of the tool. The piston may be cycled through a drive stroke and through a return stroke. The drive stroke of the fastener driving tool is generally accomplished by the dumping of pressurized fluid above the drive piston in the cylinder, and the return stroke will take place upon the exhaust of the cylinder above the drive piston. Suitable means are provided for returning the piston through the return stroke. In one commercially known embodiment, the cylinder is of the differential type, and the drive piston is also of the differential type. Pressurized fluid from the fluid reservoir of the tool is supplied intermediate the stepped diameters of the piston, thereby continually biasing the piston upwardly. Heretofore, difliculty has been experienced during the return stroke of the drive piston in that vacuum conditions are created below the piston. Communication of the cylinder below the piston with the atmosphere then results in ingestion of air from the outside. In a plant such air is frequently contaminated with dust and other undesirable material.

Moreover, it has been known commercially to employ pneumatically operated fastener driving tools to drive nails from a nail strip wherein the nails are held in spaced relation by suitable connecting material. The magazines of such fastener driving tools feed the nails into the drive track of the tool wherein each nail is severed from the remainder of the strip during the drive stroke of the tool.

Difficulty has heretofore been experienced in the feeding and loading of such nail strips. Moreover, although the cost of the magazine is not great, the competitive situation requires that the fastener driving tools, including the magazines, be manufactured at the lowest possible cost.

Accordingly, it is an object of the present invention to provide a new improved fastener driving tool which overcomes the above mentioned difficulties.

Another object of the present invention is to provide a new and improved fastener driving tool wherein ingestion of outside air into the cylinder is prevented during the return stroke of the drive piston.

Another object of the present invention resides in the provision of a new and improved magazine assembly for a fastener driving tool which is constructed at low cost of sheet material.

A further object of the present invention is the provision of a new and improved magazine construction which provides for positive feed of the fastener strip.

A further object of the present invention is the provision of a new and improved magazine construction wherein the fastener strips may be readily loaded within the track of the magazine assembly.

Yet another object of the present invention is the provision of a new and improved fastener driving tool wherein operation of the tool is inhibited upon depletion of the supply of fasteners within the magazine assembly.

In accordance with these and other objects, there is provided an improved fastener driving tool for use with a fastener strip including spaced fasteners joined by suitable connecting means. The tool may be of a generally known type comprising a housing including a structure defining a fluid reservoir and additional structure defining a cylinder and a driving track. A drive piston is provided within the cylinder slidably mounted therein and including a fastener driving assembly slidably mounted in the drive track. The upper end of the main cylinder above the piston may be'selectively supplied with the pressurized fluid for moving the piston through a drive stroke to actuate the fastener driver blade and for exhausting the major portion of the fluid from that end of the main cylinder during a return stroke of the piston. One such valve arrangement is more thoroughly illustrated and described in US. patent application Ser. No. 632,590, filed Apr. 21, 1967 by Novak, now Pat. No. 3,498,517 granted Mar. 3, 1970, and assigned to the same assignee as the present invention. The other end of the cylinder adjacent the drive track is exhausted to the atmosphere. Trigger means are connected to actuate the piston through a drive stroke; one such trigger means is more fully described and illustrated in copending application Ser. No. 767,020, filed Aug. '26, 1968, by O'bergfell, now abandoned, and assigned to the same assignee as the present invention. In addition, it has been customary to provide a safety means normally inhibiting actuation of the piston through its drive stroke and releasable by engagement of the safety means with a work piece. Suitable means are provided for returning the drive piston through its return stroke.

In accordance with the present invention, there is provided a positive head of pressurized fluid below the piston during its return stroke, thus preventing ingestion of contaminated outside air into the working cylinder of the tool.

In accordance with another feature of the present invention, there is provided an improved magazine assembly for feeding fasteners to the drive track of the tool, and in the illustrated embodiment is particularly adapted to advance nail type fasteners. The magazine assembly includes a carrier formed of sheet metal and having an upper track for supporting the heads of the nails. The carrier is open at its top rear to provide for insertion of a fastener strip. There is provided an improved fastener pusher movable through a slot in the side wall of the magazine so as to cam over an inserted strip of fasteners upon retraction so as to pick up the last one of the fasteners in the strip. A pusher biasing spring biases the pusher and fasteners forwardly so as to present the fasteners one at a time to the drive track of the tool.

-In accordance with another feature of the present invention, the pusher of the magazine assembly is provided with a latch projection movable against a stop on a member of the safety lever so as to prevent depression of the safety means upon engagement by a workpiece if the fasteners within the magazine assembly have been depleted to a predetermined point. Thus, the fastener driving tool will be inhibited from further actuation upon depletion of the supply of fasteners within the magazine assembly.

For a better understanding of the present invention, reference may be had to the accompanying drawings wherein:

FIG. 1 is a side elevational view, partially broken away, of the improved fastener driving tool and magazine assemy;

FIG. 2 is a side elevational view, broken away, of the fastener driving tool of FIG. 1, drawn to a larger scale;

FIG. 3 is a sectional perspective view of the drive piston of FIG. 2;

FIG. 4 is a bottom sectional view of the piston and cylinder of FIG. 2, taken along the line 4-4 of FIG. 2;

FIG. 5 is a fragmentary top cross sectional view of the fastener driving tool and magazine of FIG. 1, taken along the line 55 of FIG. 1;

FIG. 6 is a cross sectional front view of the magazine assembly of FIG. 1, taken along line 66 of FIG. 1;

FIG. 7 is a cross sectional rear elevational view of the magazine assembly of FIG. 2 taken along line 77 of FIG. 2;

FIG. 8 is a plan view of the magazine assembly of FIG. 1, taken along line 88 of FIG. 1;

FIG. 9 is a cross sectional plan view of the magazine assembly of FIG. 1, taken along line 99 of FIG. 1;

FIG. 10 is a cross sectional elevational view of the magazine assembly of FIG. 1, taken along line 1010 of FIG. 1;

FIG. 11 is a cross sectional elevational view of the magazine assembly of FIG. 1, taken along line 1111 of FIG. 1;

FIG. 12 is a cross sectional view of the resilient mounting of the magazine assembly to the fastener driving tool taken along line 12-12 of FIG. 1;

FIG. 13 is a perspective view of the fastener pusher of FIG. 1;

FIG. 14 is a cross sectional plan view of the magazine assembly of FIG. 1, similar to FIG. 5, but illustrated with a depleted supply of fasteners in the magazine;

FIG. 15 is a fragmentary cross sectional plan view of the magazine assembly illustrated with the pusher carnmed over a strip of fasteners;

FIG. 16 is a fragmentary cross sectional view of the magazine of FIG. 15, taken-along line 1616 of FIG. 15; and

FIG. 17 is an exploded perspective view of the nose end of the fastener driving tool and magazine assembly.

Referring now to the drawings, there is illustrated a new and improved fastener driving tool constructed in accordance with the present invention and referred to generally by the reference numeral 20. The tool 20 is adapted to be operated by compressed fluids supplied from a convenient source, such as an air compressor (not shown), and the tool is portable in the sense that an operator may manipulate the tool by hand into the proper position for driving fasteners into a workpiece.

The tool includes a housing 22 preferably from a durable lightweight metal, such as aluminum or the like, to facilitate manual handling, and the housing comprises a vertically extending, hollow forward head chamber 24 and a rearwardly extending handle 26 defining a reservoir for containing a supply of compressed fluids supplied from the Cir fluid source. The head chamber 24 is adapted to contain and support a reciprocally movable piston member, FIGS. 2-4, which is slidable within a main cylinder 32 and a rodlike fastener driving element or driver blade 34 secured to the lower end of the piston member in any suitable manner, as by means of a nut 36. The lower end of the head chamber 24 and main cylinder 32 is closed by a removable lower end cap or end member 3 8 provided with a central opening 38a permitting sliding movement of the driver blade 34 and further providing communication of the lower end of the main cylinder 32 under the piston member with the atmosphere. The piston member 30 moves upwardly in the cylinder 32 on a returnstroke and is then driven rapidly downwardly on a power or drive stroke to drive a fastener into the workpiece. A donutshaped cushion 40 of resilient material such as rubber is mounted in the lower end of the cylinder 32 to absorb the shock of the piston member 30 as it reaches the end of the drive stroke.

The end cap member 38 defines a drive track 46 within a nosepiece for accommodating the reciprocal movements of the driver blade 34 and for guiding fasteners, such as nails 48 or the like, which are fed from a strip 49 into the drive track of the fastener driving tool 20.

In order to feed the nails 48 one at a time into the drive track 46 and to contain a supply of the nails 48 which are fastened together into the strip 49 by carrier strips 50 formed of suitable material such as plastic, the tool 20 includes a magazine assembly 56 according to the present invention and supported at its forward end to the end cap 38 and the nosepiece 44 and supported intermediate its length from the housing 22 by resilient mounting assemblies 5 8 and 60, best illustrated in FIGS. 6 and 12, respectively. The mounting assembly 58 includes a mounting bolt and nut assembly 62 rigidly secured to the magazine assembly 56, and passing through an opening 64 in the nosepiece 44, being mounted rel ative therewith by a pair of resilient spacers 66. A sleeve 68 and washer 70 provide a bearing and compression surface for the bolt and nut assembly 62.

The mounting assembly 60 includes a mounting nut and bolt assembly 72 extending through an opening 74 in the rear portion of the housing 22, and fastening a mounting bracket 76 secure to the magazine assembly 56 through suitable resilient spacers 78. A sleeve 80 and washers 82 provide the proper surface for bearing and compression of the resilient spacers 78. The bracket 76 is fastened to the magazine assembly 56 in any suitable manner, as by bolts 79, FIG. 9.

The magazine assembly 56 extends from the nosepiece 44 at an angle to the reservoir handle 26 forming an open area therebetween to permit easy gripping of the tool by the handle. The nails 48 contained in the magazineassembly 56 are advanced forwardly therein into the drive track 46 through a slot or feed opening 84 in the rear base of the nosepiece 44 and are then driven into a workpiece by the downward drive stroke of the driver blade 34 which is imparted by the piston member 30.

The main cylinder 32 is supported at its lower end by the cap member 38 and the internal wall surface of the lower end of the head chamber 24, and an O-ring seal 88 is provided to seal between the other surface of the inner'cylinder and the facing surface of the lower end of the head chamber 24. Another O-ring seal 90 intermediate the head chamber 24 and main cylinder 32 defines an inner air chamber 92 for providing a control signal to a valve assembly 100. Above the seal 90- the internal diameter of the head chamber 24 increases somewhat in order to provide an annular air space or air chamber 102 which surrounds the upper end of the main cylinder 32 and is in communication with the reservoir 26 for receiving a continual supply of compressed fiuid to operate the piston member 30. The inner cylinder is open at its upper end, FIG. 2, and is formed with a lower section 32a having an internal diameter which is slightly smaller than the diameter of an upper section 32b. The piston 30 is constructed like a spool and has a lower end flange 30a slidable in the lower cylinder section 32a, and an upper end flange 30b slidable in the upper cylinder section 32b, and a cylindrical central stem 300 of reduced diameter integrally connecting the upper and lower end flanges 30a and 30b. Accordingly, an angular piston chamber 106 is formed around the stem 300 within the cylinder 32 and is closed at opposite ends by the end flanges 30a and 30b of the piston member.

Compressed fluid is continuously supplied to the piston chamber 106 around the stem 30c by means of several large ports 108 in the inner cylinder 32 adjacent the junction of the upper and lower sections thereof. Sealing between the piston chamber 106 and the upper and lower ends of the cylinder 32 is obtained by means of O-rings 1'10 and 112 mounted on the piston flanges 30a and 30b, respectively. Because of the upper piston flange 30b being slightly larger in diameter than the lower flange 30a, whenever pressurized fluid is present in the annular piston chamber 106, the piston member 30 will have an upward resultant force applied thereto, tending to move or bias the piston member 30 and driver blade 34 upwardly on the return stroke to the upper position illustrated in FIG. 2 at the top end of the cylinder 32.

The upper end of the head chamber 24 is formed with an integral shoulder 118 having a cylindrical bore surface in concentric alignment with the longitudinal axis of the piston member 30 and slightly larger in diameter than the upper open end of the main cylinder 32. A removable upper cap member 120 is mounted on the upper end of the head chamber 24 and the cap member is formed with a relatively large cylindrical poppet valve chamber 122 having a lower end in communication with the upper end of the head chamber '24 and slightly larger in diameter than the bore surface. The cap member 120 also includes a small, second cylindrical valve chamber 124 in concentric alignment with and communicating with the upper end of the larger poppet chamber 122.

In order to control the flow of pressurized fluid from the air chamber 102 into and out of the upper end of the cylinder above the piston member 30, a pressure operated slidable poppet valve member 130 is in sliding movement within the valve chamber 122 in the cap member 120. The poppet valve member 130 comprises a cylindrical disk 130d having an upper peripheral edge slidable against a cylindrical wall surface of the valve chamber 122 and an O-ring 132 is mounted on the disk 130d to effect a good seal between the valve member and the chamber side wall. The under side of the cylindrical disc 130d is recessed to accommodate a circular sealing gasket 134 which seats against the upper open end of the inner cylinder 32 when the valve is closed, shown in FIG. 2. The poppet valve member 130 also includes a downwardly depending cylindrical skirt slightly smaller in diameter than the diameter of the valve chamber. The skirt is slidable within the bore in the upper end of the head chamber 24 of the tool housing and an O-ring seal 136 is mounted on the skirt to seal against the bore surface as the poppet valve moves up and down. The poppet valve member 130 also includes an upwardly extending, small diameter hollow stem 130a which is slidable within the small valve chamber 124 of the cap member 120, and an O-ring 138 is mounted on the stem 130a to seal against the cylindrical walls of the valve chamber. A central passage 13% is formed in the valve member 130 and the gasket 134 so as to communicate between the upper end of the cylinder 32 and the upper end of the valve chamber 124. The poppet valve member 130 is normally biased downwardly to close against the upper end of the cylinder 32 by means of a spring 140 which is seated within the bore of the hollow stem 130a and the upper end of the spring bears against a circular exhaust sealing gasket 142 mounted in the upper end of the valve chamber 124, and by fluid pressure above the disk 13011 of the poppet valve.

In operation the valve member 130 is controlled by pneumatic fluid acting upon its upper surface. 'More specifically, there is provided a cylinder valve passage 146 communicating with the upper surface of the poppet valve member 130 in the valve chamber 122. The cylinder valve passage 146 is connected through the valve assembly to the supply of pressurized fluid in the reservoir 26 so as normally to bias the valve member 130 downwardly to the position illustrated in FIG. 2. Pressurized fluid in the inner chamber 102 will act on the lower outer surface of the valve member 130 exerting an upward force on the valve member 130. However, the net resultant force on the valve member 130 is down, maintaining the valve member 130 in its closed position. When it is desired to fire the fastener driving tool 20 through a drive stroke, the air in the valve chamber 122 is exhausted through the cylinder valve passage 146 to the atmosphere. At this time the air pressure in the air chamber 102 will be effective to snap the valve member 130 upwardly, closing the stern 130a against the sealing gasket 142 and simultaneously dumping pressurized fluid from the air chamber into the top of the cylinder, driving the piston 30 downwardly through a drive stroke. Upon completion of the drive stroke, pressurized fluid will once again be admitted into the valve chamber 122, driving the valve member back to the position illustrated in FIG. 2, and displacing the stem 130a of the valve member 130 from the sealing gasket 142. The upper end of the main cylinder 32 above the piston 30 will now be exhausted through the passageway 13012 and exhaust passageway 148 formed in the cap member 120. Since pressurized fluid in the piston chamber 106 establishes a resultant upward force on the piston 30, the piston will now be driven upwardly through its return stroke.

The valve assembly 100 may be of any known type and in the illustrated embodiment is similar to that described and claimed in the above-mentioned Obergfell application and therefore need not be fully herein described. Briefly, the valve assembly 100 is of the type including a trigger valve assembly 150 having a manually depressible trigger 152 for firing the tool 20. In addition, the valve assembly 100 is controlled through a safety valve which prevents firing of the tool 20 when the nosepiece 44 thereof is out of engagement with a workpiece. To this end, there is provided a safety valve member 154 engageable with the valve assembly 100 through a valve stem 156. The safety valve member 154 is guided for vertical movement by a safety valve pin 158 and is biased downwardly to the position illustrated in FIG. 1 by a safety valve spring 160. When the safety valve member 154 is in its lowermost position, as illustrated in FIG. 1, firing of the fastener driving tool 20 through a fastener driving stroke is inhibited; however, when the safety valve member 154 is depressed upwardly by engagement with a workpiece, the valve assembly 100- is conditioned to permit actuation of the fastener driving tool 23 drive stroke by depression of the trigger 152.

The illustrated valve assembly 100 is of the single cycle type, wherein the drive piston 30 is actuated through a drive stroke by depression of the trigger 152 and automatically cycles through a return stroke, regardless of whether the trigger 152 has been released. To this end, the air chamber 92 is pressurized through a plurality of metering ports 166 in the side wall of the main cylinder 32 whenever the lower flange 30a of the piston 30 moves below the ports 166 during its drive stroke. The air chamber 92 is placed in communication with a cycling valve control of the valve assembly 100 through a signal port 168. Thus, as the piston 30 approaches the end of its drive stroke, a signal is transmitted to the valve assembly 100 effecting return of the piston 30.

Although the operation of the valve assembly 100 is more fully described in the above-mentioned Obergfell application, briefly it will be understood that with the safety valve member 154 depressed by engagement with a workpiece, depression of the trigger 152 is effective to exhaust the space above the cylinder valve 130 to the atmosphere, dumping air into the upper end of the main cylinder 32 and causing the piston 30 to move through a drive stroke. As the piston 30 reaches the end of its drive stroke, a signal will be transmitted through the signal passage 168 to the valve assembly 100, and the valve assembly 100 will re-establish communication through the passage 146 between the upper end of the cylinder valve 130 and the fluid reservoir, pressurizing the valve chamber 122 and closing the main valve 130. The differential force acting on the piston 30 within the piston chamber 106 will now move the piston 30 through a return stroke.

in accordance with one feature of the present invention, a metered amount of pressurized fluid from above the piston 30 will be directed below the piston 30 through passageways 172 so as to prevent a vacuum condition forming below the piston 30 during the return stroke. Such a vacuum condition is undesirable not only in its retarding of the return stroke of the piston, but because of ingestion of contaminated atmospheric air through the clearance 38a. The passageways 172 are sufliciently restrictive so that seepage of air therethrough has no undesirable effect upon the drive stroke of the piston, but effective to pressurize the chamber below the piston 30 during the return stroke. Thus, during the return stroke of the piston 30, the major part of the pressurized fluid above the piston 30 will be exhausted through the cylinder valve in the cap member 20 and specifically through the passageway 13% and exhaust the passageway 148. However, a small portion of the pressurized fluid from above the piston 30 -will be permitted to escape through the restricted passageways 172.

Referring now to the construction of the magazine assembly 6, the magazine assembly includes a sheet metal housing or carrier 176, generally elongated, somewhat rectangular in cross section, but as illustrated in FIG. 6, having an enlarged upper end 176a defining a track means for carrying the head 48a of the nails 48. A slotted tube 178 of generally C-shaped cross section is positioned within the enlarged upper end 1760 forming the track of the magazine assembly 56. The slotted tube 178, how ever, extends only through the forward portion of the carrier 176, and the carrier 176 has the upper rear portion of its surface open beyond the rearward termination of the tube 178 as at 17612. The upper edges of the sheet metal carrier 176 along the open slot 17% are formed into reverse bends 176c, FIG. 11, and the slotted tube 178 is flared upwardly and outwardly at the forward edge of the opening 17612 as indicated at 1782. Thus, the opening v176b provides a means for loading strips 49* of nails by shoving them into the carrier 176 with their heads 48a within the slotted tube 178 and pushed forwardly into the magazine assembly 56-.

To continuously bias a nail strip 49 forwardly through the magazine 56, there is provided a pusher 180 slidably mounted on the carrier 176 of the magazine assembly 56 and projecting through a longitudinally extending slot 182 in the side wall of the carrier 176. To slidably mount the pusher 180, the carrier 176 is formed with an outwardly extending boss 184 along the slot 182, and the pusher 180 is provided 'With a vertically extending rail portion 186, best illustrated in FIG. 13, slidable within the inside of the carrier 176 along the slot 182 and is further provided with a pair of vertically extending ears 188 externally of the carrier 176. The forward edge of the rail portion 186 is slightly concave, as at 1860, to general 1y conform to the shank contour of a nail fastener, and is engageable with the last nail in a nail strip 49 during the forward movement of the nail strip. A pusher biasing spring 190 is mounted for winding on a spool 191 supported on a sleeve 192 secured to the nosepiece 44 of the tool 20 by a suitable screw 194 and is fastened to the pusher in a suitable manner as by the pin 196. The biasing spring biases the pusher toward the drive track of the tool 20. When unwound from the spool 191, the biasing spring 190 bows inwardly in cross section toward the strip 49 of nails, as indicated at 190a, FIG. 6, thereby aiding in positioning and guiding the nail strip.

In use, it is understood that a nail strip 49 is inserted into the magazine 56 with the nail heads resting in the slotted tube 17 8 and is moved forwardly toward the drive track. The pusher may then be moved rearwardly against the action of the biasing spring 190, and the clearance between the pusher 1'80 and the sides of the carrier 176 defining the slot 182 permits the pusher to cam away from the nail strip, as indicated in FIG. 15, and pass over the inserted nails until the rear end of the strip is reached. As the pusher is released, the forward edge 186a of the pusher 180 will pivot inwardly to engage the shank of the last nail in the strip. Thus, the biasing spring 190 now biases the pusher and engaged nail strips forwardly toward the drive track in the tool.

In accordance with another feature of the present invention, operation of the fastener driving tool is prevented when the supply of nails in the magazine 56 is depleted. T 0 this end, the pusher 180 is provided with a cam 200 having a rearwardly and upwardly inclined cam surface 200a, best illustrated in FIG. 13, extending sidewardly from the carrier 176 of the magazine assembly 56. As the pusher 180 moves forwardly toward the drive track of the tool 20, the cam 200 will engage a cam follower 202 secured to a latch member 204. The latch member 204 is pivotally mounted on the sleeve 192 and is provided with a projection 204a engageable against a generally horizontally extending shoulder 206 defining a stop surface of the safety valve member 154. A torsion spring 208 normally biases the latch member 204 out of interference with the vertical movement of the safety valve member 154. However, when the pusher 180 approaches the drive track of the tool 20, as illustrated in FIG. 14, the cam 200 engages the cam follower 202 and pivots the latch member 204 into interfering fit with the stop surface 206' of the safety valve member 154 and thus prevents depression of the safety valve member 154, thereby inhibiting further operation of the fastener driving tool 20 until additional nails are loaded into the magazine 56.

A chaff deflector 212 of somewhat horseshoe shape is positioned just rearwardly of the drive track to prevent the carrier strip material 50 being projected.

What is claimed and desired to be secured by Letters Patent of the United States is:

1. A fastener driving tool for use with a fastener strip including a plurality of spaced fasteners joined by connecting means, which tool comprises a housing including a structure defining a main cylinder and a drive track, drive piston means slidably mounted in said main cylinder and including a fastener driver slidably mounted in .the drive track, means including a trigger means for cycling said piston selectively through drive and return strokes, safety means normally positioned in a safety position inhibiting actuation of said piston through its drive stroke and operated to a drive position by engagement with a workpiece to permit piston actuation, said safety means including an element movable on operation of the safety means, from said safety position to said drive position a magazine assembly carried by said housing for supplying a strip of spaced fasteners to said drive track, said magazine assembly including a fastener pusher and means biasing said pusher against said strip toward said drive track, and a pivoted mechanism normally biased to a first position and pivoted to a second position by engagement with the pusher when the number of fasteners is reduced to a given value, said mechanism in its second position mechanically locking said element against movement from said safety position to said drive position to prevent operation of said safety means hetween said positions, means mounting said mechanism for pivotal movement about an axis extending generally in the same direction as the direction of movement of the fastener driver said element including a vertically movable member provided with a stop surface, and said mechanism including latch means out of a locking relation with said stop surface in said first position, and said pusher including means for camming said latch means into locking position with said stop surface in said second position.

2. A fastener driving tool for use with a fastener strip including a plurality of spaced fasteners joined by connecting means, which tool comprises a housing including structure defining a main cylinder and a drive track, drive piston means slidably mounted in said main cylinder and including a fastener driver slidably mounted in the drive track, means for cycling said piston selectively through drive and return strokes, a magazine assembly carried by said housing formed of sheet metal into a generally rectangular cross section with an enlarged upper end defining a track means for supporting the heads of nail type fasteners, including a carrier generally elongated in cross section, said carrier having a slot extending along one side wall, pusher means extending through said slot having projections within said carrier slidably mounting said pusher on the side wall of said carrier, a biasing spring biasing said pusher toward said drive track, sufiicient clearance being provided between said pusher and said carrier that said pusher will cam away from an inserted fastener strip in said magazine until the rear end of said strip is reached, and resilient mounting structure interconnecting said housing and said magazine assembly providing for shock absorbing mounting for said magazine assembly.

3. A fastener driving tool for use with a fastener strip including a plurality of spaced fasteners joined by connecting means, which tool comprises a housing including structure defining a main cylinder and a drive track, drive piston means slidably mounted in said main cylinder and including a fastener driver slidably mounted in the drive track, means for cycling said piston selectively through drive and return strokes, a magazine assembly carried by said housing formed of sheet metal into a generally rectangular cross section with an enlarged upper end defining a track means a generally tubular structure slotted at the bottom positioned in said track means for supporting the heads of the nail type fasteners, said magazine including a carrier generally elongated in cross section, said carrier having a slot extending along one side wall, pusher means extending through said slot having projections within said carrier slidably mounting said pusher on the side wall of said carrier, and a biasing spring biasing said pusher toward said drive track, suificient clearance being provided between said pusher and said carrier that said pusher will cam away from an inserted fastener strip in said magazine until the rear end of said strip is reached.

4. A fastener driving tool as set forth in claim 3 where in said track means and said tubular structure terminate forwardly of the rear end of said carrier to provide for loading of the fasteners through the upper rear of the magazine assembly.

5. A fastener driving tool for use with a fastener strip including a plurality of spaced fasteners joined by connecting means, which tool comprises a housing including structure defining a main cylinder and a drive track, drive piston means slidably mounted in said main cylinder and including a fastener driver slidably mounted in the drive track, means for cycling said piston selectively through drive and return strokes, a magazine assembly carried by said housing formed of sheet metal into a a generally rectangular cross section with an enlarged upper end defining a track means for supporting the heads of nail type fasteners, including a carrier generally elongated in cross section, said carrier having a slot extending along one side wall, pusher means extending through said slot having projections within said carrier slidably mounting said pusher on the side wall of said carrier, and a biasing spring biasing said pusher toward said drive track, sufficient clearance being provided between said pusher and said carrier that said pusher will cam away from an inserted fastener strip in said magazine until the rear end of said strip is reached, said carrier including a longitudinal boss along said slot, and said pusher including projections within said carrier along said boss providing for slidable mounting thereof.

References Cited UNITED STATES PATENTS 3,086,207 4/1963 Lingle et a1 227130 3,172,124 3/1965 Kremiller 227123 X 3,198,412 8/1965 Roosa 227- X 3,253,760 5/1966 Doyle et a1. 227-120 3,353,737 11/1967 Howard et al. 227 X GRANVILLE Y. CUSTER, JR., Primary Examiner U.S. Cl. X.R. 227l20, 136 

